As a former Assistant Attorney General in charge of the Antitrust Division at the DOJ during the Bush II years, Barnett was very loud about his pro-merger stance.

During his tenure, the DOJ approved 100% of the 46 mergers it reviewed, including Sprint/Nextel, AT&T/BellSouth, XM/Sirius, Verizon/MCI, and Verizon/Alltel.

Barnett repeatedly made the case that most antitrust cases were brought to defend the interests of rival companies, not to protect competition, and that such cases ultimately hurt innovation.

There are lots of juicy quotes Barnett gave over the years to that effect, but here's a particularly good one:

If the government is too willing to step in as a regulator, rivals will devote their resources to legal challenges rather than business innovation. This is entirely rational from an individual rival’s perspective: seeking government help to grab a share of your competitor’s profit is likely to be low cost and low risk, whereas innovating on your own is a risky, expensive proposition. But it is entirely irrational as a matter of antitrust policy to encourage such efforts.

So yeah, this guy is an unlikely champion for Expedia in the fight against Google.

Update: Barnett never opposed a merger but his record actually does demonstrate some prior uneasiness about Google's market position, as he moved against the Google-Yahoo search advertising deal. After the two companies abandoned the deal, Barnett said: "The arrangement likely would have denied consumers the benefits of competition – lower prices, better service and greater innovation."